The invention concerns a filtering and interference suppression device for an electric motor.
More specifically the invention concerns a device for filtering and interference suppression, particularly of the broad-band, high-frequency type, for an electric motor supplied by voltage that could be as high as at least 60 V.
Brush-and-commutator electric motors, particularly those that drive such equipment as windshield wipers or heating and ventilation equipment, produce interference over wide frequency bands. Such interference may disturb electronic equipment in its vicinity. In effect, it can, for example, cause the untimely activation of a switch controlled by an electronic system.
Developments in electronic equipment make it possible to produce more compact and higher performance electronic circuits, but they remain susceptible to interference particularly at high frequencies. To solve such problems, there are interference suppression devices that reduce or eliminate the harmful effects of such interference.
Such known devices consist primarily of filters composed of a capacitor, one terminal of which is connected to a strip conductor electrically powering a brush, and the other terminal of which is connected to the electrical ground of the motor, and of a coil or choke that is interposed between the corresponding brush and the capacitor terminal connected to the strip conductor that powers the brush. Generally, the coil suppresses high-frequency interference while the capacitor suppresses low-frequency interference.
Such devices make it possible to suppress interference produced in a frequency range that extends from 150 kHz to about 100 MHz. However, the use of electric motors more often requires that the influence of interference be suppressed over a frequency range of up to several GHz.
To provide a solution to this problem, the invention proposes a filtering and interference suppression device for an electric motor comprising at least a first powering brush for an armature commutator of the electric motor, a capacitor, one terminal of which is electrically connected to a strip conductor that electrically powers the first brush powering the armature commutator of the electric motor, and the other terminal of which is electrically connected to a ground strip conductor connected to the electrical ground of the motor, characterized in that the capacitor of the filtering and interference suppression device is of the non-inductive type.
Thus, compared with filtering and interference suppression devices of the type known from the prior art, the filtering and interference suppression device according to the invention has improved performance with the same compact size. This makes it possible to retain a similar layout and the same motor volume.
According to other characteristics of the invention:
the device comprises at least a first and second powering brush for the armature commutator, each of which is connected to the electrical ground of the motor, with the interposition of a capacitor, one terminal of which is connected to a strip conductor electrically powering the corresponding brush, and the other terminal of which is connected to ground, wherein each capacitor is a capacitor of the non-inductive type;
the two filtering and interference suppression capacitors of the non-inductive type are made in the form of a double non-inductive capacitor;
each of the non-inductive capacitors is attached directly to a circuit board comprising strip conductors, which include at least one strip conductor powering the brush and one ground strip;
the circuit board is the brush-bearing board for the electric motor;
each filtering and interference suppression capacitor is of the SMC-type;
the electric terminals of each non-inductive capacitor are electrically connected and attached directly to the corresponding strip conductors;
each terminal is attached and electrically connected to the corresponding strip by soldering;
each terminal is attached and electrically connected to the corresponding strip by gluing with a conductive glue;
the device comprises at least one other capacitor interposed between the ground strip and one section of the power strip for at least one of the brushes powering the commutator located between the non-inductive capacitor and the corresponding brush;
at least one of the other capacitors is of the SMC-type;
the section of at least one of the power strips for one of the brushes powering the commutator, which is located between the non-inductive capacitor and the corresponding brush, comprises a series choke;
the device comprises a choke connected in series in the ground strip between one ground terminal of the non-inductive capacitor and the brush;
at least one of the chokes is of the high-frequency type;
at least one of the chokes is coiled, and in that it comprises at least one space that separates two juxtaposed turns of the coil;
at least one of the chokes is of the SMC-type;
it comprises a thermal protector located on the ground strip;
the device comprises at least one peak limiter mounted in parallel with the noninductive capacitor, between the ground strip and one of the conducting strips;
at least one of the peak limiters is of the SMC-type.